Many different types of X-ray apparatus are known to the art, the majority of which can only be used for certain kinds of examination. More specific kinds of examination require the use of another type of tower column, which means that the X-ray department of a modern hospital must be equipped with at least two X-ray towers in each examination room. Normally, in the majority of cases more than one examination room is required, which makes the X-ray tower investment costs very high in practice.
Furthermore, within modern health organizations there is a desire to be able to carry out at least primary or preliminary X-ray examinations locally in places where the access to X-ray equipment is more limited, e.g. in the case of Sweden in so-called primary medical welfare centres and in the U.S.A. so-called free Diagnostic Centres (FDC).
In one known ceiling supported tower or tower column which co-acts with a patient examination table there is used a telescopic link arm which is connected to the beam source and the cassette holder by means of bell-and-socket joints, e.g. so that when moving the beam source in order to set the position of an angled beam path the image receptor located in the cassette holder will accompany the movement of the beam source. However, another cassette holder must be used when wishing to take pictures with a horizontal beam path. Furthermore, in this case it is necessary to remove the link arm, which means a further complication. Another circumstance which complicates the procedure still further resides in the impossibility of sustaining a centered beam path, thereby requiring the beam path to be repeatedly adjusted, which is a time-consuming and laborious task.
Another drawback characteristic of this and other known X-ray towers is that the path of the beam is brought into the desired position by the operator through manipulation of the beam source itself, this source normally being located relatively high above floor level, which means that when adjusting the position of the beam the operator has to work above shoulder height and adopt an uncomfortable and unsuitable working position.
In other kinds of X-ray towers which co-act with a patient examination table, for example a BRS-type tower (Basic Radiographic System according to WHO's Specification) there is used a wheeled mobile examination table in the form of a unit which is separate from the tower. However, in this case there is a risk of the tower and the table colliding when moving the table or the tower in order to make adjustments.
The object of the invention described in U.S. Pat. No. 3,743,843 (Reser) is to provide an X-ray tower structure which can be used more universally. The tower or column structure of this published specification includes a yoke which can be swung about an axis and which supports an examination table and a column carrying a beam source. The yoke also carries a separate coupling means, designated a "selector", the purpose of which is to enable tomographs to be taken, i.e. when the table top is displaced linearly, the beam source will perform predetermined pivotal movements which enable tomographic section photographs to be taken. The table can be removed from the yoke, whereupon the coupling means will no longer fulfill a function. However, it is often beneficial to allow a patient to remain on the table while using the X-ray tower to take pictures of another patient or to take side picture on the same patient lying on the table with a horizontal beam path.
DE-C-751 140 (Pohl) describes an X-ray tower which is separate from a floor-supported examination table. A coupling means is provided to connect a swing arm to the table. The tower is supported by the ceiling and presumes the provision of a depending tower section on each side of the table. These depending tower sections, however, impede the operator in his work. The table can be swung to a vertical position, which in many cases creates unnecessary complications.
Other examples of X-ray towers forming part of the known prior art are found described in U.S. Pat. No. 3,302,022 (Brenner et al), U.S. Pat. No. 3,927,326 (Kunne et al) and GB-A-631 289 (Poittewin).